Antenna feed system



Patented May 4, 1943 Nils E. Lindenblad', Rocky Point, N'. to RadioCorporation of America,

of Delaware Y., assignor a corporation Application June 8, 1940, SerialNo. 339,468

' Claims.

This invention relates to electrical transmission systems and, moreparticularly, to a system for feeding a load, such as an antenna system,simultaneously with energy from a plurality of transmitters operating atdifferent frequencies.

One of the objects of the present invention is to enable a plurality ofsources of oscillations operating at different frequencies to feed thesame load system simultaneously over different branch circuits in such amanner that there is no reaction between the sources over a wide rangeof frequencies.

A further object of the invention is to provide an arrangement forcoupling a pair of independent single-sided transmission lines to asingle transmission line carrying the energy from both of saidindependent lines without interaction between the independent lines.

' Still a further object of the present invention is to enable fourtransmitters operating at different frequencies to feed a turnstile'antenna without interaction between the transmitters.

In accordance with a feature of the invention there is employed betweenOne transmitter and an intermediate loop circuit a transformer forenergizing the intermediate circuit in a balanced or .push-pullrelationship. The intermediate loop circuit may comprise a pair ofbalanced transmission lines each having a line conductor surrounded by agrounded shield. Across the intermediate circuit is connected a halfwave loop c rcuit with the second transmitter connected to its midpoint.Energy from the second transmitter is thus introduced into the balancedor intermediate circuit in a push-push or in-phase relationship. I

An output transmission line is then connected to the intermediatecircuit at such point that the lengths of line from the output line tothe points of introduction of energy from the two transmitters differ byan amount which is an odd, multiple of half waves for the firsttransmitter and an even and adjacent multiple of half waves for thesecond transmtter. In this way the push-pull voltages feeding into thedifferential length lines, when these differ in length by an Oddmultiple of half waves, add up correctly for feeding into the s ngleline utilization circuit.

The push-pull voltages also add up equally correct at a frequency atwhich the differential length lines differ in length by an even multipleof half waves.

he present invention further contemplates utilizing a phase quadraturetype of utilization circuit or load in the way disclosed in my 00-pending application No. 338,177, filed May 31, 1940, in combination withthe circuits described above to feed the power from four transmittersinto'a single load. In accordance with this aspect of my invention, atumstile antenna'of the type shown in my copending application,SerialNo.

208,573, -filed May 18, 1939, now Patent No.

2,239,724, issued April 29, 1941, may be simultaneously energized withpower from four independent transmitters.

Further objects, features and'advantage of the present invention willappear from the following detailed description which is accompanied by adrawing in which Figure 1 shows an embodiment of the invention, whileFigure 2 shows a modification and further development of the form shownin Figure 1.

Referring, now, to Figure 1, there is shown a single-sided concentriccable or transmission line composed of an outer sheath 5 and an innerconductor and energized from transmitter A. I have also shown a pair oflines constituting an intermediate coupling circuit and adapted to beenergized in a push-pull relationship from transmitter A, one of saidline's being composed of an outer sheath 25 and an inner conductor 26and the other being composed of an outer sheath 35 l and an innerconductor 36. The outer sheaths 5, 25 and 35 may be grounded if desired.The inner conductor 26 is directly connected to inner conductor 6 and istherefore energized in the same relationship as the inner conductor 6.The I other inner conductor 36 is directly connected to the end of thesheath 5 of the single-sided line from transmitter A and is thereforeenergized in phase opposition to the inner conductor 26. In order tocompletely uncouple the last quarter wave section of the singletransmission line 5,

6 from the remainder of the same so that one side of the balancedcircuit is not shorted, I have provided an outer shell 7 surrounding theend of sheath 5. The'shell I has a length equal to a quarter of the meanoperating wavelength and is connected to sheath 5 of the singletransmission line at its end remote from the end of sheath 5. The lengthof the conducting path of the outer surface of sheath 5 is of suchlength that the point of connection of 36 at the free end of sheath 5 iselectrically freed from the outer conductor of the transmission line 5,6as far as radio frequency potentials are concerned. This eii'ect is dueto the fact that the length, of the conducting path including the outersurface of sheath 5 is substantially equal to a quarter wavelength atthe operating frequency of transmitter mission line from A and, pedanceconductor 36. take place from the current flowing along the outersurface of sheath since any current .flowing along the inside of theouter shell I is equal and of opposite direction. Thus it will be seenthat at the frequency for which the junction is designed the balancedline will not be subject to any unbalancing effects from the connectionto the single line. This condition is, however, true only when thesurrounding section approximates a quarter of the length of theoperating wave. If the frequency is changed or if the operatingfrequencyis widely modulated some current will lealr' over the edge ofthe single transmission line, sheath 5 and the push-pull output circuitwill be unbalanced. In order to overcome this effect and maintainperfect balance over a wide frequency band, I employ a second quarterwave shell section arranged in an end-on relationship with the outershell 1; Within the second shell section I is an inner conductor i5having the same diameter as the outer diameter of sheath 5 of the singletransmission line. Though I have referred to shells l and i1 separatelyforconvenience in description, it should be understood that in practiceit may be found more convenient to form them in one continuous piece.Theinner therefore, presents a distinctly high im-- conductor i5 isconnected at its inner end to the center conductor 5 of the single lineand, also, to the center conductor 26 of one of the balanced lines. Theother end is electrically connected to the end of shell II. The pointsof connection, and

the dimensions of the parts are so chosen, that the junction isperfectly symmetrical with respect to a center plane perpendicular tothe axis of shells I, i1. Ordinarily, shell l1 has the same diameter asshell I and conductor i5 has the sam diameter as sheath 5. with thisconstruction it will be seen that looking from the pushpull line towardthe junction along either con ductor 26 or conductor 36, an exactlysimilar set of conditions is encountered. Therefore, for a widefrequency band orfor frequencies varying widely from the frequency forwhich the Junetion is designed, the reactive drain on conductor 38 due.to an improper length of shell 1 is duplicated by an equal drain onconductor by shell portion H.

v From the foregoing description it will be seen that transmitter Afeeds conductors 25, in a push-pull relationship through a single-sidedline 5.

In order to simultaneously feed the same balanced push-pull lines from asecond transmitter .B, a pair of conductors i3, i5 is connected to theadjacent ends of shell 5 and conductor IS. The length of each of theconductors i6, i6 is equal to a quarter'of the mean operating wavelengthof the system. These conductors are connected to the central conductorof a single-sidedtranstransmitter B composed of central conductor 6' andan outer sheath 5'. It will be seen that there is in effect a half waveloop connected across the adjacent ends of conductors 26 and 36. Such a.half wave loop will, of course, not adversely affect the operation ofthe circuit as far as transmitter A is concerned. The energy fromtransmitter B is fed to conductors 25 and 36 through exactly equivalentlengths of line and the resultant energy is therefore in an in-phase orpush-push relationship.

Since it is desired to feed the energy from both transmitters to a loadthrough a single transmisthereto at the point of connection of IFurthermore, no radiation can anced lines.

sion line 30, a loop 31 is placed in one of the balthe connections fromelements 5 and iii to the inner conductor of a single transmission line30 have a differential length which is an odd multiple of a halfwavelength for the frequency of transmitter A and an even and adjacentmultiple of a half wavelength for transmitter 13. Thus, the push-pullvoltages on conductors 26 and 36 from transmitter A add up correctly forfeeding into transmission line 30. Likewise, the pushpush voltages onconductors 25 and 36 from transmitter l3 add up in a correctrelationship for feeding intotransmission line 30. Furthermore, anyenergy at the frequency of transmitter A reflected back from the antennais of an incorrect wavelength to enter transmission line 5', 6 fromconductors i6, I6, in an in-phase relationship and a similar situationexists with respect to energy from transmitter B in transmission line 5,5.

Figure 2 shows a further development of the present invention which iscapable of feeding the energy from four transmitters into a singleturnstile antenna of the type referred to above without permitting anyinteraction between the separate transmitters. The construction of theelements within boxes I0 in Figure 2 is the same as that shown withinbox In in Figure 1 and the operation thereof may be understood byreferring to the detailed disclosure in Figure 1 and the deunit similarto that described with reference to Figure 1 is provided. The energy intransmission lines 225 and 235 comprises the energy from transmitters Aand B in a push-push relationship and energy from transmitters A, B in apushpull relationship. Since, in this embodiment, it is desired toobtain a phase quadrature relationship between the energies at theutilization end of transmission lines 225 and 235, a phase shifting loop331 having a length equal to a quarter of the mean operating wavelengthis introduced in one of the transmission lines. While it is shown intransmission line 225 it is obvious that it may equally well be placedin line 235.

Since the turnstile antenna 350 requires two sets of push-pull voltagesmutually in phase quadrature with each other and each of transmissionlines 225 and 235 are each single-sided lines carrying energy in phasequadrature, it is only necessary to terminate each line in a couplingcircuit for transforming each of these transmission lines into push-pulllines 325, 326, 335, 336. The end of transmission line 225 is surroundedby a sleeve 3 having a length equal to a half the length of the meanoperating frequency. In an end-on relationship with the transmissionline 225 and within sleeve 3" is a conductor 3i5 connected to the innerconductor of transmission line 225. Lines 325 and 326 are connected tothe adjacent ends of conductor 3i5 and 305 and are thereby energized inphase opposition. The operation of the coupling circuit whereby anyinactive unbalance is compensated is the same as described withreferenceto the structure within box in in Figure 1 wherein trans- Theloop 31 has such length that 2,818,287 mission line 5, 6 is connected totransmission lines 25, 25 and 35, 36. A more complete analysis may beobtained by reference to my copending application, Serial No. 276,193,filed May 27, 1939, now

1 Patent No. 2,231,839, issued Feb; 11, 1941.

A similar coupling circuit is connected to the end of transmission line235 and supplies pushpull energy to conductors 335 and 336. Theturnstile antenna 350 is indicated merely by a pair of crossed dipoles.Opposite ends of-one dipole are fed from transmission lines 326 and 325while opposite ends of the other dipole are fed from lines 335 and 336.Since the energy inthe'two dipoles is in a phase quadrature relationshipa rotating field will be radiated.

While I have shown four transmitters feeding a single tiered turnstileantenna, it should be clearly understood that the turnstile antenna canbe of the multiple type to obtain increased vertical directivity.Furthermore, additional transmitters can be coupled to the antenna inthe same way as outlined for transmitters A, A and B, B.

While I have shown and particularly described several embodiments of myinvention, it is to be distinctly understood that my invention is notlimited thereto but that further modifications within the scope of myinvention may be made.

I claim:

1. In combination, a first single transmission line having an outersheath and an inner 'conductor, and having a first source ofoscillations connected thereto, a pair of transmission lines. aconnection from the inner conductor of said single line to a conductorof one of said pair of i lines, a connection from the sheath of sa dsingle line to a conductor of the other of said pair of lines, an outershell surrounding the end portion of said single line, said shell beingconnected to of the mean operating wavelength from the end of saidsingle line, and a balancing circuit including an inner conductorconnected to the inner conductorof said single line and having adiameter equal to the of said single line and an outer shell having adiameter equal to the diameter of the first outer shell and connectedthereto, the inner conductor and outer shell of said balancing circuitbeing connected together at a distance equal to a quarter of the meanoperating wavelength from said connections, a second single transmissionline having an outer sheath and an inner conductor, and having a secondsource of oscillations connected thereto, a connection from its innerconductor to each of said pair of lines, said connections each having alength equal to a quarter of the length of the mean operatingwavelength, a single output circuit connected to the end of said pair oflines, said pair of lines having a differentiallength which is an evenmultiple of a half wavelength of said first source and an odd andadjacent multiple of said second source.

2. In combination, a pair of sources of oscillations of difierentwavelengths, a firstconcentric line coupled to a first one of saidsources and having an outer sheath and an inner conductor, a balancedpair of concentric transmission l'nes, each having an outer sheath andan inner conductor, a connection from the inner conductor of said firstline to an inner conductor of one of said pair of lines, a connectionfrom the end of the sheath of said first line to the inner conductor ofthe other of said' pair of lines, an outer shell surrounding the end ofsaid single line and said sheath at a distance equal to a quarterdiameter of the outer sheath line coupled to a having an outer sheathand an inner conductor,

second line, said its junction with said vpair of lines, said shellbeing connected to the outer sheath of said single line at a distanceequal to a quarter of the mean wavelength from the end of said sheath, asecond concentric line coupled to the second of said sources,connections from each of the inner conductors of said pair of 'saidlines to said second line, said last connections each having a lengthequal to a quarter or the mean operating wavelength, said pair of lineshaving difierent lengths and being connected together at their otherend, the wavelengths of said pair of sources being so related that thedifierential length of said pair of lines is an even multiple of a halfwavelength of said first source and an adjacent and odd multiple of ahalf wavelength of said second source.

3. In combination, a pair of sources of oscillations of diiferentwavelengths, a first concentric line coupled to a first one of saidsources and having an outer sheath and an inner conductor, a balancedpair of concentric transmission lines, each having an outer sheath andan inner conductor, a connection of said first line to an innerconductor of one of said pair of lines, a connection from the end of thesheath of said first line to the inner conduc tor of the other of saidpair of lines, an outer shell surrounding the end of said single lineand its junction with said pair of lines, said shell being connected tothe outer sheath of said single line at a distance equal to a quarter ofthe length of said first source from the end of said sheath, a secondconcentric line coupled to the second of said sources, connections fromeach of the inner conductors of said pair of said lines to said lastconnections each having a a quarter of the wavelength of said firstsource, said pair of lines having different lengths and being connectedtogether at their other end, the wavelengths of said pair of sourcesbeing so related that the difierential length of said pair of lines isan even multiple of a half wavelength of said first source and anadjacent and odd multiple of a half wavelength of said second source. 1

4. In combination, a pair of sources of oscillalions of difierentwavelengths, a first concentric first one of said sources and a balancedpair of concentric transmission lines, each having an outer sheath andan inner conductor, a connection from the inner conductor of said firstline to an inner conductor of one of said pair of lines, a connectionfrom the end of the sheath of said first line to the inner conductor ofthe other of said pair of lines, an outer shell surrounding the end ofsaid single line and ferential length of I multiple of a'half wavelengthof said first source and an adjacent and odd multiple of a halfwavelength of said second source.

5. In combination, a pair of sources of oscillations of differentwavelengths, a first concentric li-ne coupled to a first one ofsaid'sources and from the inner conductor each having an outer .lengthfrom having an outer sheath and an inner conductor, a balanced pair ofconcentric transmission lines,

sheath and an inner conductor, a connection from the inner conductor ofsaid first line to an inner conductor of one of said pair of lines, aconnection from the end of the sheath of said first line to the innerconductor of the other of said pair or lines, an outer shell surroundingthe end of said single line and its junction with said pair of lines,said shell being connected to the outer sheath of said single line at adistance equal to a quarter of the length of said first source from theend of said sheath, a pair of connections of a length equal to a quarterof the length of said first source from ach of said connections to thesecond of said source, said pair of lines having different lengths andbeing connected together at their other end, the wavelengths of saidpair of sources being so related that the differential length of saidpair of lines is an even multiple of a half wavelength of said firstsource and an adjacent and odd multiple of a half wavelength of saidsecond source.

6. In combination, a, pair of sources of oscillations of differentwavelengths, a first concentric line coupled to a first one of saidsources'and having an outer sheath and an inner conductor, a balancedpair of concentric transmission lines, each having an outer sheath andan inner conductor, a connection from the inner conductor of said firstline to an inner conductor of one of said pair of lines, a connectionfrom the end of the sheath of said first line to the inner conductor ofthe other of said pair of lines, an outer shell surrounding the end ofsaid single line and its junction with said pair of lines, said shellbeing connected to the-outer sheath of said single line at a distanceequal to a quarter of the mean wavethe end of said sheath, and abalancing circuit including an inner conductorhaving a diameter equal tothe diameter of the outer sheath of said single line connected to theinner conductor 'of said single line and an outer shell having adiameterequal to the diameter of said first outer shell and connected thereto,the inner conductor and outer shell of said balancing cirv cult beingconnected together at a distanc equal to a, quarter of the meanoperating wavelength from the end of said first line, said pair of lineshaving different lengths and being connected together at their otherend, the wavelengths of said pair of sources being so related that thedifferential length of saidpair of lines is an even multiple of a halfwavelength of said first source and 'an adjacent and odd multiple of ahalt wavelength of said second source.

7. In combination, a pair of sources of oscillationsoi differentwavelengths, a first concentric line coupled to a first one or saidsources and having an outer sheath and an inner conductor,

a balanced pair of concentric transmission lines,

each having an outer sheath and an inner conductor, a connection fromthe inner conductor of-said first line to an inner conductor of one ofsaid pair of lines, a connection from the end or the sheath of saidfirst line to the inner conductor of th other of said pair of lines, anouter shell surrounding the end or said single line and its junctionwith said pair of lines, said shell being connected to the outer sheathof said single line at a. distance equal to a quarter of the length ofsaid first source from the end or said sheath, and a balancing circuitincluding an innerconductor having a diameter equal to the diameter orthe inner conductor of said single line andgan outer shell having adiameter equal to the diameter of said first outer shell and connectedthereto, the inner conductor and outer shell of said balancing circuitbeing connected together at a distance equal to a quarter of the lengthof said first source from the end of said first line, said pair of lineshaving different lengths and being connected together at their otherend, the wavelengths of said pair of sources being so related that thedifierential length of said pair of lines is an even multiple of a halfwavelength of said first source and an adjacent and odd multiple of ahalf wavelength of said second source.

8. In combination with means for coupling a single concentric lin havingan outer sheath and an inner conductor to a balanced circuit having apair of conductors adapted to be energized in an opposing phaserelationship, said line having a first source of oscillatory energyconnected thereto, a connection from-said inner conductor \to one ofsaid pair of conductors, a connection from the end of said outer sheathto the other of said pair of conductors and an outer shell surroundingthe end of said single line and its junction with said pair of lines,said shell being connected to said outer sheath at a distance from itsend equal to a quarter'of the length of the mean operating wavelength ofmeans for simultaneously energizing said pair of conductors in anin-phase relationship from a second source of oscillatory ener y,comprising a pair of connections to said pair of conductors from a saidsecond source, said connections each having a length equal to a quarterof the mean operating wavelength, said pair of conductors beingconnected to a single output conductor, said pair of conductors having adifierential length which is an even multiple of a half wavelength ofsaid first source and an odd and adjacent multiple of said secondsource.

9. In a transmission line circuit a pair of conductors simultaneouslyenergized at one end from one source of energy in a push-pullrelationship and from another source of energy in a push-pushrelationship, said conductors having a differential length which isequal'to an even multiple of a half wavelength of said first source andan odd and adjacent multiple of a halt wavelength of said second source,and means for connecting said conductors together at their other endsand to a load circuit whereby said load circuit is simultaneouslyenergized from both of said sources.

10. In a transmission line circuit a pair of conductors simultaneouslyenergized at one end from one source of energy in a push-pullrelationship and from another source of energy in both of said sources.

11. An oscillatory system comprising two pairs of sources of energy,each pair energizing a single transmission line through a circuit as setforth in claim 9, means for combiningthe energy from said singletransmission lines into a pair of lines in a phase quadraturerelationship, and means for obtaining push-pull energy from each 'ofsaid pair of lines.

1 2. An oscillatory system comprising two pairs of sources of energy,each pair energizing a single transmission line through a circuit as setforth in claim 10, means for combining the energy from said singletransmission lines into a pair of lines in a phase quadraturerelationship,

, length of said one frequency and an odd and adenergy from said singletransmission lines into a balanced circuit in a phase quadraturerelationship, said means comprising a pair of concentric and an innerconductor, a connection from the inner conductor of one of said singletransmission lines to each of the inner conductors of said second pairof lines, said connections having a length equal to an odd multiple,including unity, of the mean operating wavelength, a connection from aconductor of the other of said single transmission lines to the end 01one of said second -pair of lines, a connection from the other conductorof the other of said single transmission lines to the other of saidsecond pair of lines, an outer shell surrounding the end of the other ofsaid single transmission lines,-said shell being connected to the secondmentioned conductor of said line at a distance equal to a quarter of thelength of the operating wave from the end thereof, said outer shellextending beyond the end of said other line a-quarter of the meanoperating wavelength and an inner conductor within the extending portionof said shell connected to the first mentioned inner conductor of saidsecond pair of lines, said outer shell and said last mentioned innerconductor being connected together a distance equal to a quarter of thelength of the transmission lines each having an outer sheath meanoperating wavelength beyond the point of connection to said innerconductor, one of said second pair of lines being a quarter wavelengthlonger than the other whereby phase quadrature output is obtained.

14. In combination, a pair of conductors coupled at one end to onetransducer means operative at one frequency in a push-pull relationshipand to another transducer means operative at a difierent frequency in apush-push relationship, said conductors having a difi'erential lengthwhich is equal to an even multiple ot a half wavejacent multiple of ahalf wavelength of said different frequency, and means for connectingsaid conductors together at their other ends and to a third transducermeans.

15. In combination, a pair of transducer means operative withoscillations of different wavelengths, afirst concentric line coupled toa first one of said transducer means and having an outer sheath and aninner conductor, a balanced pair of concentric transmission lines, eachhavingan outer sheath and an inner conductor, a

connection from the inner conductor of said first line to an innerconductor of one of said pair of lines, a connection from the end of thesheath of said first line to the inner conductor of the other of saidpair of lines, an outer shell surrounding the end of said single lineand its junction with said pair'of lines, said shell being connected totheouter sheath of said single line at a distance equal to a quarter ofthe wavelength of "the oscillations for said first transducer means from\the end of said sheath, a pair of connectionsof a length equal to aquarter of the wavelength of the oscillations for said first transducermeans from each of said connections to the second of said transducermeans, said pair of lines having different lengths and being connectedtogether and to a third transducer means at their other end, theoperating wavelengths of said pair of transducer means being so relatedthat the difierential length of said pair of lines is an even multipleof a half wavelength of said first transducer means and an adjacent andodd multiple of a half wavelength of said second transducer means.

NILS E. LINDENBLAD.

